There are a lot of internationally recognized calculations and reporting methods and companies can hire consultants who can estimate the emissions in their end to end supply chains.

There are also calculators online that can give an example on what elements are considered, e.g. the below from UN.

https://unfccc.int/documents/271269

Morgan recently did a video on handheld milk frothers at different price points (the milk still has to be heated separately), and found even the cheapest one at $5 to produce decent foam (with proper technique). If your kids are old enough to follow instructions, they might be a decent choice? Good luck on the search!